1. Field of the Invention
The present invention relates to a process for preparing a gastrointestinal hormone from small intestine of a mammal at a high yield.
2. Description of Prior Arts
As the process for the preparation of gastrointestinal hormone, there has been a well known process in which the hormone is directly extracted from the small intestine with ethanol, dilute hydrochloric acid or the like. According to this process, however, the efficiency of the extraction of gastrointestinal hormone is extremely low, and this process cannot be used as an industrial process.
As improvements of this process, there have been proposed a process which comprises mincing the small intestine and extracting gastrointestinal hormone with hot dilute acetic acid (Japanese Pat. No. 535,068) and a process which comprises heating the small intestine in boiling water, mincing the heated small intestine and extracting gastrointestinal hormone at room temperature with dilute acetic acid (U.S. Pat. No. 3,013,944). These processes are still insufficient to use them in the mass-production of gastrointestinal hormone. In the former process, the yield of the hormone is low, because they are decomposed and inactivated at the mincing and subsequent steps by various proteases contained in the small intestine. In the latter process, since the small intestine is heated in boiling water, the protease are inactivated, but since the gastrointestinal hormone is easily soluble in water, the loss of the hormone in boiling water is extreme. For example, when the small intestine is heated in boiling water for 5 to 10 minutes, about 30 to about 40% of total secretin and about 20 to about 30% of total cholecystokinin-pancreozymin are lost in boiling water. Therefore, in both conventional methods, a considerable quantity of gastrointestinal hormone is lost in the initial stage of the preparation process.